Wood flooring composed of wpl, base and soundproof layer

ABSTRACT

Disclosed herein is a back-grooved laminate wood flooring in which a wood veneer of high pressure resin impregnation laminate (WPL) is laminated on a base selected from a vinyl chloride (PVC) resin layer, on oriented strand board (OSB), a high-density fiberboard (HDF) and a waterproof plywood. More specifically, the back-grooved laminate wood flooring comprises a WPL ( 20 ), an adhesive layer ( 40 ) and a base ( 10 ) (a polyvinyl chloride resin layer, OSB, HDF or waterproof plywood) wherein the WPL ( 20 ) includes a base-reinforcing layer ( 24 ), a natural veneer layer ( 23 ), a resin-impregnated overlay layer ( 22 ) and a surface UV coating layer ( 21 ) layered in this order from the bottom. The back-grooved laminate wood flooring further exhibits excellent soundproofing performance.

TECHNICAL FIELD

The present invention relates to a back-grooved laminate wood flooringfor an under-floor heating system in which a wood veneer of highpressure resin impregnation laminate (hereinafter, referred to as a‘WPL’) is laminated on a base selected from a polyvinyl chloride resinlayer, an oriented strand board (OSB), a high density fiberboard (HDF)and a waterproof plywood. More particularly, the present inventionrelates to a back-grooved laminate wood flooring for an under-floorheating system comprising a WPL, an adhesive layer and a back-groovedbase wherein the WPL includes a base-reinforcing layer (made ofshielding paper, high-density fiberboard or kraft paper), a resinimpregnated or not impregnated natural veneer layer, a resin-impregnatedoverlay layer and a surface UV coating layer layered in this order fromthe bottom, the back-grooved base is selected from a polyvinyl chlorideresin layer, an oriented strand board (OSB), a high-density fiberboard(HDF) and a waterproof plywood, and the WPL and the base are adhered toeach other by the adhesive layer.

BACKGROUND ART

FIG. 1 is a cross-section showing a conventional wood flooring for anunder-floor heating system in which an untreated upper natural veneerlayer 23 is laminated on a waterproof plywood layer 10′. As shown inFIG. 1, the conventional wood flooring for an under-floor heating systemin which the untreated natural veneer layer 23 is UV-coated orimpregnated in a resin. An adhesive layer 40 is interposed between thenatural veneer layer 23 and the waterproof plywood layer 10′.

Wood flooring structures in which two melamine-impregnated overlaysheets are layered to both surfaces of a natural veneer were suggested.These wood floorings have a surface strength higher than conventionalUV-coated wood floorings. However, they have problems that the naturaltexture is poor and curls are likely to occur, which negatively affectsthe quality of the finished products.

The respective layers constituting the conventional wood flooring for anunder-floor heating system are briefly explained below with reference toFIG. 1.

The waterproof plywood layer 10′ is produced by layering 5 to 7 veneerstogether using a phenol or melamine resin adhesive in such a manner thatthe grain directions of the veneers are at right angles to each other,and pressing the laminate in a press.

The upper natural veneer layer is produced by impregnating or notimpregnating a natural veneer in an impregnating resin, or impregnatingthe resin into the natural veneer under reduced or high pressure. Thesurface UV coating layer is produced by subjecting the upper naturalveneer to top, intermediate or under coating 6˜10 times using a urethaneacrylate paint in a process known in the art. Since the conventionalwood flooring for an under-floor heating system comprises the waterproofplywood layer 10′, it exhibits excellent dimensional stability againstheat and moisture.

However, since the untreated upper natural veneer has a problem of a lowdensity, the wood flooring exhibits a surface scratch resistance as lowas 0.5˜1N and an impact resistance as low as 10˜20 cm. The scratchresistance is measured by scratching using a diamond needle afterUV-coating the surface of the natural veneer, and the impact resistanceis measured by dropping a metal ball weighing 225 g onto the surface ofthe natural veneer. There is a large possibility that the conventionalwood flooring is easily impaired when laying heavyweight householdappliances on the wood flooring and using them. Accordingly, theconventional wood flooring causes consumer complaints and cannot satisfyconsumer's diverse needs. There is, thus, a need for wood flooringshaving improved physical properties.

In fact, the surface strength of the wood flooring for an under-floorheating system is measured in accordance with a common method known inthe art. For example, the scratch resistance is measured by scratchingthe surface of a test piece cut in a predetermined size from the woodflooring for an under-floor heating system at room temperature using adiamond needle and is expressed in a 0.5N unit. The impact resistance ismeasured by dropping a weight (225 g) from increasing height (by 10 cm)onto the surface of the test piece, and then the presence of damage tothe test piece is visually observed.

DISCLOSURE OF THE INVENTION

Therefore, the present invention has been made in view of the aboveproblems, and it is an object of the present invention to provide aback-grooved laminate wood flooring for an under-floor heating systemmanufactured by a WPL technique. The back-grooved laminate wood flooringthus manufactured exhibits considerably improved surface strength andnatural texture, compared to conventional wood floorings for anunder-floor heating system.

It is another object of the present invention to provide a back-groovedlaminate wood flooring for an under-floor heating system which exhibitsexcellent soundproofing performance.

In order to accomplish the above objects of the present invention, thereis provided a laminate wood flooring for an under-floor heating systemcomprising a WPL, an adhesive layer and a back-grooved base wherein theWPL includes a general UV or primer-treated UV coating layer, aresin-impregnated overlay layer, a resin impregnated or not impregnatednatural veneer layer and a base-reinforcing layer layered in this orderfrom the top, the back-grooved base is selected from a polyvinylchloride resin layer, an oriented strand board (OSB), a high-densityfiberboard, (HDF) and a waterproof plywood, and the WPL and the base areadhered to each other by the adhesive layer.

As used herein, the general UV coating layer is referred to as a layerformed by a UV coating process known in the art, and the primer-treatedUV coating layer is referred to as a layer formed by coating an aminoresin (urea, melamine or urea-melamine resin)-impregnated product, whichis a new process which has not been reported until now.

For reducing noise transmission between floors and imparting improvedsoundproofing performance, the laminate wood flooring for an under-floorheating system further comprises at least one soundproof layer laminatedin at least one position selected from (a) between the WPL and the baseand (b) under the base.

The back-grooved laminate wood flooring for an under-floor heatingsystem according to the present invention is manufactured by a methodcomprising the steps of: pressurizing a strand or fiber obtained bycutting or fibered lumber in a urea, urea-melamine, phenol, resorcinolor MDI (4,4′-dimethyldiisocyanate) resin to form a strand board orhigh-density fiberboard; layering 5 to 7 veneers together using a phenolor melamine resin adhesive in such a manner that the grain directions ofthe veneers are at right angles to each other, and pressing the laminatein a press to produce a waterproof plywood layer; impregnating anoverlay paper in a resin selected from urea, urea-melamine, melamine,phenol, acryl, polyester, unsaturated polyester, epoxy, polyvinylacetate, polyvinyl alcohol and urethane resins to produce asurface-protective paper layer (resin-impregnated overlay layer), theoverlay paper being prepared by uniformly distributing wear-resistantsilica or alumina particles in a cellulose paper; cutting natural rawlumber using a rotary lathe or slicer to produce a natural veneer layer;impregnating a kraft paper in a resin selected from urea, phenol, acryl,polyester, unsaturated polyester, epoxy, polyvinyl acetate, polyvinylalcohol and urethane resins to produce a base-reinforcing layer;pressurizing a fiber obtained by fibered lumber in a resin selected fromurea, melamine, urea-melamine and phenol resins to form a high-densityfiberboard; laying the high-density fiberboard or kraft paper, theimpregnated or not impregnated natural veneer and the overlay paper inthis order from the bottom, and pressing the layering under highpressure at high temperature to produce an upper WPL; applying a resinselected from melamine, polyurethane and epoxy adhesives onto a baseselected from a polyvinyl chloride resin layer, an OSB, an HDF and awaterproof plywood, to form an adhesive layer, adhering the WPL to theadhesive layer, and pressing the laminate under high pressure at hightemperature; and coating the resulting structure using UV light or aurethane primer, and grooving the back surface of the base.

Preferably, for the purpose of reducing noise transmission betweenfloors and imparting improved soundproofing performance, the method formanufacturing the laminate wood flooring for an under-floor heatingsystem according to the present invention further comprises the step oflaminating at least one soundproof layer in at least one positionselected from (a) between the WPL and the base (one selected from apolyvinyl chloride resin layer, an OSB, an HDF and a waterproof plywood)and (b) under the base (one selected from a polyvinyl chloride resinlayer, an OSB, an HDF and a waterproof plywood).

BRIEF DESCRIPTION THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-section showing a conventional wood flooring for anunder-floor heating system in which an upper natural veneer is laminatedon a base;

FIG. 2 is a cross-section of a laminate wood flooring for an under-floorheating system in which a WPL is laminated on a back-grooved base, inaccordance with an embodiment of the present invention; and

FIG. 3 is a cross-sectional view of another laminate wood flooring foran under-floor heating system of the present invention in which twosoundproof layers are added to the wood flooring of FIG. 2, inaccordance with another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described in more detail withreference to the following examples and accompanying drawings. However,these examples and drawings are not to be construed as limiting thescope of the invention.

A base-grooved laminate wood flooring for an under-floor heating systemaccording to one embodiment of the present invention is shown in FIG. 2.As shown in FIG. 2, the surface of an upper WPL 20 is coated using UVlight or coated with a primer-treatment followed by UV lightirradiation. The upper WPL 20 and a base 10 are adhered to each other byan adhesive layer 40.

The upper WPL 20 includes a base-reinforcing layer 24 made of at leastone material selected from shielding paper, high density fiberboard andkraft paper, a resin-impregnated or not impregnated natural veneer layer23, a resin-impregnated overlay layer 22 and a general UV coating layeror urethane type primer-treated special UV coating layer 21 layered inthis order from the bottom.

In the back-grooved laminate wood flooring for an under-floor heatingsystem in which the upper WPL 20 is laminated on the base 10 selectedfrom a polyvinyl chloride resin layer, an oriented strand board (OSB), ahigh-density fiberboard (HDF) and a waterproof plywood, the respectivelayers and the lamination procedure are explained in detail below.

The polyvinyl chloride resin layer is produced to a thickness of 1.0˜5.0mm from a composition consisting of a PVC resin, a plasticizer, a fillerand a stabilizer.

The OSB and HDF are produced by pressurizing a strand or fiber obtainedby cutting or fibered lumber in a phenol, resorcinol or MDI resin,followed by forming it. The waterproof plywood layer is produced bylayering 5 to 7 veneers together using a phenol or melamine resinadhesive in such a manner that the grain directions of the veneers areat right angles to each other, and pressing the laminate in a press.These layers exhibit little dimensional stability due to heat andmoisture and thus are suitable for use in an under-floor heating system.

Next, each layer constituting the upper WPL 20 will be described.

UV treatment of the overlay layer 22 is carried out 6˜10 times in termsof surface protection and high quality appearance. The UV coating layer21 is produced by impregnating the overlay layer 22 in an amino resin(urea, melamine or urea-melamine resin), followed by primer treatmentand UV light irradiation.

The overlay layer 22 is produced to impart surface physical properties,e.g., wear resistance and scratch resistance, to the laminate woodflooring for an under-floor heating system according to the presentinvention.

The overlay layer 22 is produced by impregnating an overlay paper in aresin selected from urea, urea-melamine, melamine, phenol, acryl,polyester, unsaturated polyester, epoxy, polyvinyl acetate, polyvinylalcohol and urethane resins in an amount of 150˜300% by weight, based onthe weight of the overlay paper, followed by drying and semi-curing inan oven at 90˜150° C. for 0.5˜4 minutes. At this time, the overlay paperis prepared by uniformly distributing wear-resistant silica or aluminaparticles in a cellulose paper having a basis weight of 20˜100 g/m².

By means of the wear-resistant particles and impregnating resin, theoverlay layer 22 exhibits a high wear resistance of 200˜20,000 timeswhen abraded with sandpaper.

The natural veneer layer 23 underlying the overlay layer 22 is producedby cutting natural raw lumber for improved natural texture of thelaminate wood flooring for an under-floor heating system according tothe present invention. Specifically, the natural veneer layer 23 isproduced by cutting natural raw lumber using a rotary lathe or slicer toa thickness of 0.3˜5 mm. For improved water resistance and hardness, thenatural veneer layer 23 may be produced by dipping a natural veneer in aresin or impregnating the resin into the natural veneer under reducedpressure, and drying and semi-curing in an oven at 80˜150° C. for 0.5˜4minutes. The resin used to produce the natural veneer layer 23 is aresin selected from urea, urea-melamine, melamine, phenol, acryl,polyester, unsaturated polyester, epoxy, polyvinyl acetate and urethaneresins in an amount of 30˜150% by weight, based on the weight of thenatural veneer.

Next, the base-reinforcing layer 24 made of shielding paper, HDF orkraft paper is produced in such a manner that the surface UV coatinglayer 21 and the overlay layer 22 are supported and the WPL is made in asheet form having a certain thickness.

The base-reinforcing layer made of HDF is produced by treating a fiberobtained from a coniferous or deciduous tree in a resin selected fromurea, urea-melamine, phenol and resorcinol resins in an amount of 4˜20%by weight, based on the weight of the fiber, followed by forming,pressing at high temperature and curing.

The base-reinforcing layer made of kraft paper is produced byimpregnating a kraft paper having a basis weight of 80˜300 g/m² in aresin selected from urea, phenol (preferably transparent phenol), acryl,polyester, unsaturated polyester, epoxy, polyvinyl acetate, polyvinylalcohol and urethane resins in an amount of 40˜150% by weight, based onthe weight of the craft paper, followed by drying and semi-curing in anoven at 80˜150° C. for 0.5˜3 minutes. Two or more sheets of the kraftpaper can be used depending on the desired thickness.

The upper WPL 20 is produced by laying the base-reinforcing layer 24made of shielding paper, high-density fiberboard or kraft paper, theresin-impregnated or not impregnated natural veneer layer 23 and theresin-impregnated overlay layer 22 in this order from the bottom,pressing the laminate in a press under 20˜100 kg/cm² at 120˜180° C. for15˜60 minutes, and cooling the laminate under the same pressure for15˜30 minutes.

The upper WVPL 20 and the base 10 are adhered to each other by theadhesive layer 40.

Examples of adhesives used to produce the adhesive layer 40 includethermosetting melamine, and thermosetting or room temperature-curableurethane and epoxy resins.

When the thermosetting melamine resin is used as the adhesive, it isapplied onto the base 10 in an amount of 80˜300 g/m² to form theadhesive layer 40. When the thermosetting or room temperature-curableurethane or epoxy resin is used as the adhesive, it is applied onto thebase 10 in an amount of 80˜250 g/m² to form the adhesive layer 40.Thereafter, the upper WPL 20 is laid on the adhesive layer 40. When thethermosetting melamine resin is used as the adhesive, the laminate ispressed under 10˜15 kgf/cm² for 1˜5 minutes and then cured. When theroom temperature-curable urethane or epoxy resin is used as theadhesive, the laminate is pressed under 10˜15 kgf/cm² for 2˜4 hours andthen cured.

The press of the base 10 and the upper WPL 20 at room temperature canminimize deformation due to heat.

FIG. 3 is a cross-sectional view of another laminate wood flooring foran under-floor heating system of the present invention in which twosoundproof layer are added to the wood flooring of FIG. 2, in accordancewith another embodiment of the present invention. As shown in FIG. 3, afirst soundproof layer 30 is interposed between the upper WPL 20 and theadhesive layer 40, and a second soundproof layer 31 underlies the base10. However, the position and number of the soundproof layers are notspecially limited.

As materials of the soundproof layers, polyvinyl chloride(PVC),polyethylene (PE), ethylene vinyl acetate (EVA), polypropylene (PP),polyurethane (PU), polyester non-woven fabrics, chloroprene rubber (CR),acrylonitrile butadiene rubber (NBR), etc., can be used. In addition,the surface of the soundproof layers can be processed by a chemicalcross-linking and foaming process or a high-pressure foaming processincluding an embossing and intaglio technique.

EXAMPLES

1. Production of Polyvinyl Chloride Resin Layer, Strand Board,High-Density Fiberboard and Waterproof Plywood Layer 10

A polyvinyl chloride resin layer was produced to a thickness of 1.0˜5.0mm from a composition consisting of a PVC resin, a plasticizer, a fillerand a stabilizer.

A strand board and a high-density fiberboard were produced bypressurizing a strand or fiber obtained by cutting or fibered lumber ina melamine resin, followed by forming it. A waterproof plywood layer 10was produced by layering 5 to 7 veneers together using a melamine resinin such a manner that the grain directions of the veneers were at rightangles to each other, and pressing the laminate in a press.

2. Production of Upper WPL 20

1) Production of UV Coating Layer 21

UV coating was carried out 6˜10 times in terms of surface protection andhigh quality appearance. As for an overlay layer impregnated in an aminoresin (urea, melamine or urea-melamine resin), UV coating was carriedout following primer treatment.

2) Production of Overlay Layer 22

An overlay layer 22 was produced by impregnating an overlay paper inurea-melamine, melamine and acryl resins, respectively, and flowed bydrying and semi-curing in an oven at 90˜150° C. for 0.5˜4 minutes. Atthis time, the overlay paper was prepared by uniformly distributingwear-resistant silica or alumina particles in a cellulose paper having abasis weight of 20˜100 g/m².

3) Production of Natural Veneer Layer 23

A natural veneer layer 23 was produced by cutting natural raw lumberusing a rotary lathe or slicer to a thickness of 0.3˜5 mm. For improvedwater resistance and hardness, the natural veneer layer 23 was producedby dipping a natural veneer in polyester resin and melamine resin,respectively, or impregnating the resins into the natural veneer underreduced pressure, followed by drying and semi-curing in an oven at80˜150° C. for 0.5˜4 minutes.

4) Production of Base-Reinforcing Layer 24 Made of Shielding Paper, HDF,Kraft Paper

A base-reinforcing layer 24 made of shielding paper, HDF or kraft paperwas produced in such a manner that the overlay layer 22 and the naturalveneer layer 23 were supported and the WPL was made in a sheet formhaving a certain thickness.

The base-reinforcing layer 24 made of shielding paper was produced byimpregnating a cellulose wood-free paper having a basis weight of 50˜150g/m² in a phenol resin, followed by drying and semi-curing in an oven at80˜150° C. for 0.5˜3 minutes. Two or more sheets of the shielding papercan be used depending on the desired thickness.

The base-reinforcing layer 24 made of HDF was produced by treating afiber obtained from a coniferous or deciduous tree in a phenol resin,followed by forming, pressing at high temperature and curing.

The base-reinforcing layer 24 made of kraft paper was produced byimpregnating a kraft paper having a basis weight of 80˜300 g/m² in aphenol resin, followed by drying and semi-curing in an oven at 80˜150°C. for 0.5˜3 minutes. Two or more sheets of the kraft paper can be useddepending on the desired thickness.

As the phenol resin used to produce the base-reinforcing layer, atransparent phenol resin was preferably used.

5) Production of Upper WPL 20

A upper WPL 20 was produced by laying the layers produced in 1) to 4)above, 1 to 3 sheets of the base-reinforcing layer, the natural veneerlayer 23 and the overlay layer 22 and the surface UV coating layer 21 inthis order from the bottom, pressing the laminate in a press under 20,40, 60, 80 and 100 kg/cm² at 130˜140° C. for 15˜60 minutes,respectively, and cooling the laminate under the same pressure for 20minutes.

3. Formation of Adhesive Layer 40 on Base 10, and Lamination of UpperWPL 20 Thereon

An adhesive layer 40 was produced by applying a thermosetting melamineresin onto the base 10 in an amount of 150 g/m². Alternatively, anadhesive layer 40 was produced by applying a room temperature-curableurethane or epoxy resin onto the base 10 in an amount of 200 g/m².Thereafter, the upper WPL 20 was laid on the adhesive layer 40. When thethermosetting melamine resin was used as the adhesive, the laminate waspressed under 12 kgf/cm² for 5 minutes and then cured. When the roomtemperature-curable urethane or epoxy resin was used as the adhesive,the laminate was pressed under 10 kgf/cm² for 2 hours and then dried at80° C. for 2 hours to manufacture a laminate wood flooring for anunder-floor heating system.

The surface physical properties of the laminate wood flooring for anunder-floor heating system (Example) thus manufactured were comparedwith those of a conventional natural veneer-decorated wood flooring foran under-floor heating system (Comparative Example). The results areshown in Table 1.

The surface strength of the wood floorings was measured in accordancewith the following common procedure. The scratch resistance was measuredby scratching the surface of a test piece having a predetermined sizeusing a diamond needle and was expressed in a 0.5N unit. The impactresistance was measured by dropping a weight (225 g) from increasingheight (by 10 cm) onto the surface of the test piece and then thepresence of damage to the test piece was visually observed. TABLE 1Example Comparative Example Scratch resistance (N) 2˜5 0.5˜1 Impactresistance (cm) 30˜80   10˜20

As is apparent from the data shown in Table 1, the surface physicalproperties of the laminate wood flooring for an under-floor heatingsystem according to the present invention were greatly improved,compared to those of the conventional wood flooring for an under-floorheating system. The scratch resistance increased to a maximum of 5N, andthe impact resistance increased to a maximum of 80 cm. These resultsindicate that the WPL technique of natural veneer greatly can improvethe surface strength and thus eliminates consumer complaints andsatisfies consumer's diverse needs.

INDUSTRIAL APPLICABILITY

As apparent from the foregoing, the back-grooved laminate wood flooringfor an under-floor heating system in which a WPL is laminated on a baseaccording to the present invention are greatly improved in scratchresistance (2˜5N) and impact resistance (30˜80 cm), compared to theconventional wood flooring for an under-floor heating system. Inaddition, the back-grooved laminate wood flooring for an under-floorheating system exhibits considerably improved natural texture by UVcoating a urethane primer onto the overlay layer impregnated in an aminoresin, and minimizes the occurrence of curls by using a (transparent)phenol resin for the base-reinforcing layer, instead of a melamineresin. Furthermore, since the back-grooved laminate wood flooring for anunder-floor heating system further comprises at least one soundproofinglayer, soundproofing performance is improved after installation.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A laminate wood flooring for an under-floor heating system comprisinga wood veneer of high pressure resin impregnation laminate (WPL), anadhesive layer and a base, wherein the WPL includes a base-reinforcinglayer impregnated in a phenol resin, a resin-impregnated or notimpregnated natural veneer layer, a resin-impregnated overlay layer anda UV or primer-treated UV coating layer layered in this order from thebottom, the base-reinforcing layer being made of at least one materialselected from a high-density fiberboard, a kraft paper and a shieldingpaper, the base is back-grooved, and is selected from a polyvinylchloride resin layer, an oriented strand board (OSB), a high-densityfiberboard (HDF) and a waterproof plywood, and the WPL and the base areadhered to each other by the adhesive layer.
 2. The laminate woodflooring for an under-floor heating system according to claim 1, whereinthe resin-impregnated natural veneer layer is produced by cuttingnatural raw lumber to a natural veneer having a thickness of 0.3˜5 mm,and dipping the cut natural veneer in a resin or impregnating a resininto the natural veneer under reduced pressure, the resin being selectedfrom urea, urea-melamine, melamine, phenol, acryl, polyester,unsaturated polyester, epoxy, polyvinyl acetate and urethane resins andused in an amount of 30˜150% by weight, based on the weight of thenatural veneer.
 3. The laminate wood flooring for an under-floor heatingsystem according to claim 1, wherein the resin-impregnated overlay layeris produced by impregnating an overlay paper in a resin selected fromurea, urea-melamine, melamine, phenol, acryl, polyester, unsaturatedpolyester, epoxy, polyvinyl acetate and urethane resins in an amount of150˜300% by weight, based on the weight of the overlay paper, theoverlay paper being prepared by uniformly distributing wear-resistantsilica or alumina particles in a cellulose paper having a basis weightof 20˜100 g/m².
 4. The laminate wood flooring for an under-floor heatingsystem according to claim 1, wherein the base-reinforcing layer made ofshielding paper is produced by impregnating a cellulose wood-free paperhaving a basis weight of 50˜150 g/m² in a transparent phenol resin, andthe base-reinforcing layer made of kraft paper is produced byimpregnating a kraft paper having a basis weight of 80˜300 g/m² in atransparent phenol resin.
 5. The laminate wood flooring for anunder-floor heating system according to claim 4, wherein two or moresheets of the resin-impregnated shielding paper, high-density fiberboardor kraft paper are alternatively used depending on the desiredthickness.
 6. The laminate wood flooring for an under-floor heatingsystem according to claim 1, wherein the resin-impregnated overlay layeris produced by impregnating an overlay paper in an amino resin selectedfrom urea, urea-melamine and melamine resins, and is coated with aurethane primer and UV light treatment.
 7. The laminate wood flooringfor an under-floor heating system according to any one of claims 1 to 6,further comprising at least one soundproof layer laminated in at leastone position selected from (a) between the WPL and the base and (b)under the base.
 8. The laminate wood flooring for an under-floor heatingsystem according to claim 7, wherein the soundproof layer is made of apolymer selected from polyvinylchloride (PVC), polyethylene (PE),ethylene vinyl acetate (EVA), polypropylene (PP), polyurethane (PU),polyester, non-woven fabrics, chloroprene rubber (CR) and acrylonitrilebutadiene rubber (NBR), and the surface of the soundproof layer isprocessed by a chemical crosslinking and foaming process or ahigh-pressure foaming process including an embossing and intagliotechnique.